Process for improving aluminum alloy



Patented July 10, 1934 UNITED STATES.

1,965,604 PROCESS FOR IMPROVING ALUMINUM LOY Alfred J. Lyon, Harshinanville, Ohio N 0 Drawing.

Application April 7, 1930,

Serial No. 442,468

13 Claims.

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of anyroyalty thereon.

My invention relates to the improvement of aluminum alloys containing copper as the principal alloying constituent with other elements in lesser amounts, such as nickel, iron, silicon, magnesium, chromium, lithium, calcium or manganese or any combination of these elements.

One object is to provide alloys of this type for use in cast and wrought parts, having improved physical properties, especially tensile strength, elongation and hardness; another object is to improve the'soundness and eliminate porosity in alloys of this type used in the form of castings that must resist pressure such as cylinder heads and other parts of internal combustion engines; a further object is to provide a method of producing these improvements in a simple and inexpensive manner. Y 9

Aluminum copper alloys are knownto be divided into two groups. The first group comprises those alloys containing from three to six per cent copper and includes numerous compositions used commercially in both the wrought and cast condition with and without heat treatment. The other group comprises those alloys containing greater than six per cent copper and are used commercially. in the cast condition with or without heat treatment;

My invention is based on the discovery that all or a part of the alloying constituents of aluminum base alloys may be incorporated into the alloys by the means of their chloride compounds thereby greatly aiiecting the hardness, strength, ductility and soundness of castings or parts made from these alloys in accordance with methods well known to the art. The efiect upon the physical properties varies with the chloride compound used, and the copper content, which may vary from three to fifteen per cent; and the properties that are obtained are different than the properties that are obtained when the metal of the chloride compound is incorporated into the alloy by the usual and known methods. I am aware that certain chlorine compounds have been used as fluxes in connection with the melting of aluminumfalloys for the purpose of cleansing the metal from impurities. My invention of course is not primarily concerned with this phase of aluminum alloy treatment, altho I recognize that in the treatment of aluminum alloys in accordance with my invention this cleansing is incidental to the modifying effect or grain refining that the compounds have upon the alloy. For example the compound NH4C1 is well known to have a cleansing effect upon aluminum and other alloys but does not produce a modifying effect as is illustrated by the following results:

Chemical composition. Copper4.3 percent, Silicon0.7 percent, Iron-4.5 percent Tensile strength lbs. per sq. m.

Elongation percent in 2 ins.

Brinell hardness With 0.5 percent ammonium c chloride 32, 400 With no additions of the aluminum-copper alloys can be increased,

and the grain structure refined, by the addition of the alkaline earth metals, barium, strontiumor calcium. I am aware that the alkaline earth metal hydroxides, alkaline earth metals, fluorides, sodamide and the oxide compounds of the alkaline earth metals when introduced into aluminum alloys containing more than six per cent copper, in the molten condition have a modifying eiiect and increase the strength hardness and ductility of castings made from these alloys. I am also aware that the alkaline earth metals, their fluoride, oxide and hydroxide compounds and certain other metals such as bismuth, antimony, boron and manganese are known to improve the strength and ductility of aluminum alloys containing substantial amounts of silicon as the principal alloying constituent when added to the molten alloy. I have found by a series of tests upon aluminum alloys containing three to six per cent copper as the principal alloyingconstituent and with small amounts of iron and silicon as impurities that metals and elements that modify and refine the grain structure of aluminum copper alloys containing more than six per cent copper or aluminum alloys containing from three? to fifteen per cent silicon as the principal alloying constituent, do not have the same efiect upon alloys of the type which are included in my invention. As an illustration I have added metallic sodium, potassium," potassium fluoride, sodium fluoride or lithium fluoride to aluminum copper alloys containing four per cent copper without improving the strength, ductility or hardness, but when I added lithium chloridein the same manner and in the same amounts to the molten alloy I obtained substan tial improvements in the strength and ductility of the alloy when cast under the same conditions as the untreated alloy. This is in accordance with the known facts concerning the modification of aluminum alloys for the purpose of refining the grain structure and improving the physiample in which metallic oxides are reduced by aluminum. I have incorporated manganese for example into aluminum copper alloys by this principle by using the compound manganese di- Oxide but it has no modifying effect when added in this manner.

In the preferred practice of the present invention, a copper-aluminum alloy is prepared in the usual manner by melting aluminum ingot which contains small amounts of iron and silicon as impurities, together withthe copper and all or a part of other alloying constituents in the form of commercially pure metals or in the form of rich alloys of the alloying constituents with aluminum. When the alloy is molten and has reached a temperature of approximately 700 degrees centigrade, I introduce the chloride compound of one or more of the alloying constituents as described hereinafter.

Chloride compounds are-hydroscopic and vbe-- fore introducing them to the molten aluminum, they must be dried by heating to a temperature of approximately 100 C. for several hours and then crushed to break down lumps and crusts that form during the drying treatment, or they may be melted and poured into sticks or other forms of convenient size for introducing into the molten metal.

The chloridesare then incorporated with the molten aluminum alloy by wrapping weighed quantities in aluminum foil or paper and holding it beneath the surface of the molten metal. For this purpose a section of wrought iron pipe open at both ends is welded to an iron rod or handle, in such a manner that the section of pipe, approximately 4 inches in length and 1% inches in diameter, may be lowered beneath the surface of the molten metal in a horizontal position.

The chloride compounds in this manner are held beneath the surface of the metal until the reaction is completed. Stirring or agitation of the metal by mechanical meansis not necessary as the reduction of the chlorides is accompanied by .considerable agitation of the me an evolution of chlorine gas.

The chloride compounds can also be incorporated into the aluminum or aluminum alloys by other methods, such as pouring the molten metal into a crucible preheated with the chloride compounds in the bottom, or by stirring the pewdered and dried salts into the molten metal. However, these methods do not produce as satisfactory results and I prefer to use the method first described.

I have found that certain of the metal chlorides added to the aluminum alloys in the molten condition in accordance with this method caused an improvement in physical properties, but when L remelted without further addition of these chlorides, the gained strength, hardness and ductility are partially lost and in some instances cause the properties to be inferior to the untreated alloy. As an illustration, the following results were obtained on standard test specimens cast from an alloy containing 4.3 percent copper, 0.5 percent iron, and 0.7 percent silicon, in green sand heat treated by a method well known to the art.

Elonga- 0am Bnnell bard- Remarks percent Chloride added Percent Aa treated. 1st remelt. Zndremelt.

As treated. lat remelt. 2nd remelt.

As treated. 1st remelt. 2nd remelt.

As treated. 1st remelt. 2nd remelt. As treated. 1st remelt.

As treated. 1st remelt.

As treated. 1st remelt. 2nd remelt.

A! heated. lat remelt. 2nd remelt.

As-mixed. lat remelt.

By adding certain of the metal chlorides in additional amounts upon remelting the properties of the alloy can be improved and restored to values equal to or greater than those obtained by the first addition of the metal chloride. Nickel, Lithium and copper chlorides are especially useful for this purpose, but further additions of iron, zinc, chromium, or tin chlorides adversely afiect the strength and hardness. This is illustrated by the results tabulated in the following table, obtained on standard specimens cast in sand and heat treated from an aluminum alloy containing 4.3 per cent copper and small amounts of silicon and iron.

Elom. Tensile Brinell Chloride added Percent strength 2 ,hard- Remarks PSI- mm nes o. 25 as. an a o 18 m remelt. o. 25 40.5% 9.0 a) 2ndremelt. o. 50 39,400 9. 0 81 3rd remelt. a 50' as, 900 10.0 at remelt.

0.25 31, aoo 1. s 19 m remelt. 0.25 38.450 a1 so 2ndramelt. o. 50 31,050 1. a 10 are remelt. a 50' 41,830 11.0 82 4th remelt (1 25 35, 900 7. 3 75 1st remelt. o. 25 31.350 9. s 14 2nd remelt. o 50 35, sec 0. o 14 3rd remelt. o. 50' 33,020 1.1 1: 4m remelt.

(125 52,250 1.0 12; 1st remelt.

, on 37,875 as 122 Zndremelt o. 50 as, mo 0. a no 3rd remelt a so 21, 250 111 an rem'elt o. 25 40, 850 9. o 81 m remelt o. 25 31,100 :1. 0 so 2nd o. 50 so, 050 5. 0 19 3rd remelt. o. 50' 36, e. 0 m an remelt.

' Total chloride adding in prom of ramelting equals 1.5 pa out.

be used to obtain the optimum physical properties alloy containing 4.3 percent copper, 0.69percent silicon and 0.51 percent iron. The manganese incorporated into thealloy was determined by chemical analysis to be of the weight of. its

chloride compound.

Manganese Tensile strength lbs. Elongation Brinell percent per sq. in. percent in 2 hardness A B O A B C A B C The results shown in column A and C are for the purpose of illustrating the improved properties I obtain by using the chloride compound, since it is well known to the art that the method of casting andthe type of specimen has a profound efiect on the physical properties. The results in columns A, B and C were obtained upon the same type test specimens, sand cast and heat treated in the same manner. The manganese was incorporated into the alloy from which the results in column A were obtained by the usual method" of using a manganese rich alloy containing 10 percent manganese and approximately percent aluminum. The manganese was incorporated into the alloy, from which the results in column C were obtained by means of manganese dioxide added'to the molten alloy before pouring. I have found that the best results for a manganous chloride modified alloy of this type are obtained when manganous chloride is used in the amounts from about .4 to .5 percent.

As another example of improving the properties of eliminating the defects from certain alloys of the type that are, the subject of my invention, such as eliminating porosity, I melt an aluminum alloy containing 4 percent copper, 1 percent magnesium, and 2 percent nickel in the usual manner and when the molten metal has reached a temperature of 700 C., I introduce nickelous chloride or cupric chloride or a mixture of nickelous and cupric chlorides in amounts greater than .75 per cent. Less than .7- per cent nickelous chloride does not produce the result desired. Other chloride compounds may be used for this purpose, but where zinc is used, for example, the strength of the alloy at high temperature is adversely affected.

By introducing the chloride compounds of lithium or manganese or a combination thereof into the molten alloy in the manner already described and preferably in amounts from about .25 per cent to'l percent, the grain structure and the size of the particles of the alloying constituents are reduced and refined and consequently go into solid solution more quickly thus shortening the period of the usual heat treatment.

The alloys produced. according to my invention may be utilized for any kind of casting, and such castings may be worked as by rolling, extruding,

metal molds or by and hardness of a chill casting is increased to a marked degree by rolling or forging.

chilling and that the strength From these and other experimental have discovered that each of the chloride compounds added to-the molten aluminum alloy of this type affect the physical properties of the heat treated castings in a manner that cannot be obtained by the addition of the metal of the compound; by the reduction of other compounds containing the metal; by the additions of metal in the primary state; or by treating the metals with chlorine gas obtained by the reduction of such compounds as ammonium chloride.

. Therefore, in carrying out my invention in the preferred manner, I select one of the chloride compounds or a mixture of two or more chloride compounds that produce the special combination of properties such as strength, hardness or strength and ductility and soundness that may be aluminum and containing 3% to 15% copper as the principal alloying constituent, and thereafter incorporating in the molten alloy a material containing manganese chloride.

3. A process for producing aluminum-copper alloy, which consists in the steps ofmelting together a mixture consisting predominately of aluminum and containing at least 3% copper as the principal alloying constituent, and thereafter incorporating in the molten alloy a material containing manganese chloride.

4. A process for producing aluminum-copper alloy, which consists in the steps of melting together a mixture consisting predominately of aluminum and containing not more more than 15% copper as the principal alloying constituent, and thereafter incorporating in the molten alloy a material containing manganese chloride.

5. A process for producing aluminum-copper alloy, which consists in the'steps of melting together a mixture consisting predominately of aluminum and containing 3% to 15% copper as the principal alloying constituent, and thereafter introducing into the molten alloy a material containing manganese chloride in an amount sufllcient to improve the physical properties of the alloy.

6. A process for producing aluminum-copper alloy, which consists in the steps of melting together a mixture consisting of approximately 97% aluminum and the balance consisting mostly of copper, and thereafter adding to said molten mixture a chloride of manganese in a relatively limited amount.

'7. A process for producing aluminum-copper alloy, which consists in the steps of melting aluminum containing iron 0.5% and silicon 0.7% together with copper 4.3 and'there'after introducing into the molten alloy manganese chloride from about .25% to about 50%.

8. A process for producing aluminum-copper alloy, which consists in the steps of melting aluminum containingiron 0.5% and silicon 0.7% as the basic constituent together with copper 4.3%, and thereafter adding to said molten alloy manganese chloride of at least 25%.

9. A process for producing aluminum-copper alloy, which consists in the steps of melting aluminium containing iron 0.5% and silicon 0.7% as the basic constituent together with copper 4.3%, and thereafter adding to. said molten alloy manganese chloride of about .50%.

10. A process for producing aluminum-copper alloy, which consists in the steps of melting together a mixture consisting of aluminum as the base, copper in substantial amounts, and iron and silicon in lesser amounts, and thereafter introducing into the molten alloy a chloride of any one of the elements of the group, copper, iron, manganese, nickel, tin, chromium and lithium.

7 11. A process for producing alumimnn-coppet' alloy, which consists in the steps of melting together a mixture consisting predominately or aluminum, copper 3 to 15% and iron and silicon in lesser amounts and thereafter adding to the said molten mixture a material containing nickel chloride.

12. A process for producing aluminum-copper alloy, which consists in the steps of melting aluminum containing iron about .5% and silicon about .'I%, together with copper about 4.3%, and thereafter introducing into the molten alloy a chloride of nickel in a relatively limited amount.

13. A process for producing aluminum-copper alloy, which consists in the steps of meltin aluminum containing iron about .5% and silicon about 37%, together with copper about 4.3%, and thereafter adding to said molten alloy about 25% nickel chloride.

ALFRED J. LYON. 

